Fresh water supplies are becoming alarmingly scarce in the face of a growing population that demands a high standard of living. Water availability is impacted by both increased discharge of waste into the environment and faster depletion of clean, subsurface sources. In response, it is projected that wastewater reuse (gallons/yr) will necessarily double by 2035. Impaired water such as wastewater requires due diligence for removal of disease-causing pathogens; again, due to increased and concentrated anthropogenic contaminants.
Microbiological pathogens, viruses, protozoa bacteria and organic contaminants in particular, are of great concern in municipal and at-the-source water supplies, particularly as these sources become scarcer and more polluted with increasing population coupled with increasing industrialization of developing countries. Filtration (over coagulation for instance) remains a method of choice for water treatment for both municipal plants and at-the-source or home treatment, given the ease of use, rapid treatment rate, and re-usability filter media (thus reduced cost). However, size-exclusion filtration is challenging for small pathogens such as viruses. Therefore, filtration by chemical affinity is an attractive option. Self-cleaning membranes or surfaces are also particularly attractive for water treatment, in that biofouling is a considerable challenge. Furthermore, the ability to clean filtration media extends its use and lifetime.
The primary issues relative to microbiological contaminants are 1) viruses are virtually impossible to filter by size exclusion due to their small diameter, and 2) biofouling of membranes is a ubiquitous problem, regardless of the type of water that is treated. Finally, the public is increasingly wary of using tap water, let alone treated waste-water for domestic use. Incidents such as the 1993 Milwaukee cryptosporidium outbreak have eroded public confidence in municipal water quality. However, confidence would build with development of highly effective, state-of-the-art treatment technologies.
What is needed is a method and system for treating fluid streams that is less expensive and more effective than current methods and systems.
One advantage of the present disclosure is to provide an improved fluid treatment method and system.
Another advantage of the present disclosure is to provide a fluid treatment method and system that effectively removes pathogens and/or organic material from municipal water.
Another advantage of the present disclosure is to incorporate in a membrane a coating for preventing or removing biofouling of the membrane and extending its useful lifetime.
Another advantage of the present disclosure is to provide alternatives to titanium dioxide as photocatalytic materials for coating surfaces.
Another advantage of the present disclosure is to provide a layering method of affixing photocatalytic agents to surfaces, using materials that are resistant to photocatalytic oxidation.
Other features and advantages of the present disclosure will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the disclosure.
Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.